ClickHouse/dbms/src/AggregateFunctions/IBinaryAggregateFunction.h

#pragma once

#include <IO/WriteHelpers.h>
#include <AggregateFunctions/IAggregateFunction.h>

namespace DB
{

template <typename T, typename Derived>
class IBinaryAggregateFunction : public IAggregateFunctionHelper<T>
{
private:
    Derived & getDerived() { return static_cast<Derived &>(*this); }
    const Derived & getDerived() const { return static_cast<const Derived &>(*this); }

public:
    void setArguments(const DataTypes & arguments) override final
    {
        if (arguments.size() != 2)
            throw Exception{
                "Passed " + toString(arguments.size()) + " arguments to binary aggregate function " + this->getName(),
                    ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH};

        getDerived().setArgumentsImpl(arguments);
    }

    void add(AggregateDataPtr place, const IColumn ** columns, const size_t row_num, Arena * arena) const override final
    {
        getDerived().addImpl(place, *columns[0], *columns[1], row_num, arena);
    }

    static void addFree(const IAggregateFunction * that, AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena * arena)
    {
        static_cast<const Derived &>(*that).addImpl(place, *columns[0], *columns[1], row_num, arena);
    }

    IAggregateFunction::AddFunc getAddressOfAddFunction() const override final { return &addFree; }
};

}